1. Field of the Invention
The present invention relates generally to the refrigeration industry. More particularly, the present invention relates to an apparatus used for the removal of solid particles and water from refrigerant fluids and gases. Most particularly, the present invention relates to an improved filter-drier having a replaceable tubular-type filter element, and a simplified construction.
2. Discussion of the Related Art
It is widely recognized in the refrigeration field that contaminants are present in the various fluid and gas circuits of refrigeration systems. These contaminants can include moisture, dirt, acids, sludge and varnish, and are generated from various sources including initial manufacturing debris, corrosion, compressor wear, desiccant granules, and overheating conditions.
Most commonly, acids, sludge and varnish are produced during unusual elevated, high temperature, or overheating situations. Thus, moisture and dirt are of the most concern under normal operating conditions, and most filter driers in the art are directed to removing water and solid particulates.
Water or moisture is always present in refrigeration systems. Acceptable limits vary from one unit to another, and from one refrigerant to another. Moisture is harmful even if xe2x80x9cfreeze upsxe2x80x9d do not occur. And therefore it is desirable to keep the moisture level as low as possible.
Solid particulates such as dirt, oxides, scale, sludges, flux and metallic particles are frequently found in refrigeration systems. Numerous metallic contaminants such as cast iron dust, rust, scale, steel, copper and brass chips can damage cylinder walls, bearings, and plug capillary tubes or thermostatic expansion valve screens. In addition to mechanical damage and xe2x80x9cplug upsxe2x80x9d, these contaminants catalyze chemical reactions that contribute to decomposition of the refrigerant-oil mixtures at elevated temperatures, and thus, it is also desirable to remove as much dirt as possible from refrigeration systems.
As a result, efforts have been made in the art to remove water and solid particulate contaminants using various devices. However, there are limitations to the effectiveness of these current filtration techniques.
Fiber glass pads and wire mesh screens have typically been used to remove solid particulants in refrigerant. Due to their construction, they have very little propensity to remove water. These pads and screens have been typically flat, and circular in shape, and located at the outlet of a housing. While this shape has advantage for fabrication costs, the effectiveness of the filtration performance has been limited. The filtration surface area of the circular shape is equal to or less than the cross-sectional area of the housing.
The results of this relatively small filtration surface can evolve in two ways. First, if the filter pads are designed to retain very small particles, which is desired for the protection of the system, the flow restriction through the pads will be very high, and the life will also be very short because of the fast contamination build-up.
Alternatively, if the filter pads are designed to have low flow restriction, the retention of the desired small particles will not occur, and the protection of the system will be compromised.
Desiccants have been used for many years to remove water and are generally constructed in two forms. Firstly, desiccant beads (approximately 0.10xe2x80x3 in diameter) have been put into various forms (flat beds, hollow cylinders, etc.) by using materials, such as wire mesh, or perforated steel sheet, to create the desired configuration. This construction, while giving large surface areas for water removal, has very limited filtration capacity due to the large flow path channels through the bead matrix. Also, due to the loose form of the bead bed, the beads can rub against the retaining structure, as well as each other. This rubbing action can dislodge particles from the beads, and become a contaminant within the refrigeration system.
Alternatively, desiccants have also been rigidly molded into various shapes by using a combination of binders, temperature, and pressure, and are typically referred to as a desiccant core. The desiccant cores offer improved filtration characteristics due to the use of smaller desiccant granules, and their rigid form. The combination of small desiccant granules being held together creates a matrix which provides solid particulate retention capability. However, the solid particulate can be dislodged from the molded core and become a contaminant. This particulate can be generated from abrasion with other components during assembly, shipping damage, and residue from the desiccant core molding manufacturing process.
While such a filter-drier is generally satisfactory in operation, it still suffers from the aforementioned problems of limited filter area. In addition, replacing the desiccant cores is a fairly complicated operation. Thus, those skilled in the art continued to search for an improved filter-drier with a simplified structure, and increased filtration effectiveness.
The present invention solves the long standing problems in the art by providing a filter-drier with a core-type construction in place of the previously used coreless construction. A hollow support core is sealingly attached at one end thereof about an aperture in an end cap, thus providing communication with the interior of the hollow support core. The other end of the hollow support core is sealingly closed by a closure member having an aperture or protuberance to permit fastening an opposing end cap to the other end of the hollow support core. A tubular filter is placed over the hollow support core. One or more of the known molded desiccant cores are placed over the tubular filter and held in place between the end caps. Thus, filtration area is greatly increased, and a simplified construction is provided.
Thus, one of the objects of the present invention is to overcome the shortcomings of conventional filter-driers.
Another object of the present invention is to provide an improved filter-drier having a greatly increased filtration area.
A further object of the present invention is to provide a simplified construction for a filter-drier.
A still further object of the present invention is to provide a filter-drier which is more economical to manufacture.
A further object of the present invention is to provide a filter-drier having a tubular filter in place of the circular screen filter known in the prior art.
Further objects and advantages of the present invention will be apparent from the following description and appended claims, reference being made to the accompanying drawings forming a part of the specification, wherein like reference characters designate corresponding parts in the several views.